Magnetic field sensor devices are widely used in sensor applications for contactless sensing of magnetic fields in many automotive and industrial applications. For example, in automotive applications a Hall effect device may be used to measure wheel speed in an automatic braking system (ABS) speed sensor, by measuring the speed of magnetic domains embedded in the wheel. In such an example, if a magnet approaches a stationary Hall effect device then the Hall effect device will measure an increase in the magnetic field. The frequency at which the magnetic field increase is measured allows for the speed of the wheel to be determined.
Typically, magnetic field sensor devices are configured to measure the magnetic field components along a single axis. For example, a lateral Hall plate comprised within a semiconductor die may be configured to measure a magnetic field component along an axis perpendicular to the surface of the semiconductor die. Alternatively, a vertical Hall plate comprised within a semiconductor die may be configured to measure a magnetic field component along an axis parallel to the surface of the semiconductor die. Because magnetic field sensor devices are only able to measure the magnetic field components along a single axis (e.g., an in-plane axis parallel to a plane or an out-of-plane axis normal to the plane), measurement of an out-of-plane angle is difficult.
Often measurement of an out-of-plane angle is done using a combination of different types of magnetic field sensor devices configured to respectively measure in-plane field components and out-of plane field components. By decomposing a magnetic field into one component perpendicular to a surface and another component parallel to the surface, an out-of-plane angle can be calculated as the angle between the two components.
For example, FIG. 1 illustrates an exemplary prior art magnetic field sensor 100 configured to measure an out-of-plane angle θ of a magnetic field {right arrow over (B)}. The magnetic field sensor 100 comprises a semiconductor die 102, comprising a lateral magnetic field sensor 104 (e.g., an ordinary Hall effect device) and a vertical magnetic field sensor 106 (e.g., a vertical Hall effect device). The lateral magnetic field sensor 104 is configured to measure a vertical magnetic field component 108 perpendicular to the horizontal “top” surface of the semiconductor die 102. The vertical magnetic field sensor 106 is configured to measure a horizontal magnetic field component 110 parallel to the horizontal “top” surface of the semiconductor die 102.
A processing unit may be configured to receive the measured vertical magnetic field component 108 and horizontal magnetic field component 110, and based thereupon to compute magnetic field components along a plurality of directions (e.g., along the x, y, and z axis). However, the resulting computed magnetic field components are sensitive to the tolerances of both types of sensors and therefore is limited by the tolerances of the less accurate of the two sensor types.